This application claims the priority of Germany, filed Dec. 22, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a multistation press having several slides which can be moved up and down and which are equipped with tools for forming workpieces, and a transport arrangement for transporting the workpieces between the stations.
DE 44 18 417 A1 describes a transfer arrangement in a forming machine, in which a cross traverse mutually connects two mutually opposed carriages which can be moved on rails. In order to permit that one carriage runs ahead of the other carriage in the transport direction, the cross traverse is equipped with a length compensation device.
A multistation press having a transport arrangement for transporting workpieces which has several cross traverses is also described in WO 96/26025. In that case, each cross traverse consists of two parallel rails that requires very high control-related expenditures for a slidable holding device for workpieces which is mounted thereon.
An object of the present invention is to further improve a multistation press having a transport arrangement such that the alignment of the workpieces to be transported is ensured in any arbitrary orientation in the space while the operating mode is simultaneously reliable.
According to the invention, this object is achieved by a multistation press in which the two ends of the cross traverse are connected by way of cardan joints with the respective lever arrangements.
As a result of the length compensation device according to the invention, with the tube element mounted on one lever arrangement and the interior element mounted on the other lever arrangement, the cross traverse can be oriented in any direction in the space without causing high control-related expenditures. The interior element moves with respect to the tube element and thus compensates differences between the position of the lever arrangement at one end of the cross traverse and the lever arrangement at the other end of the cross traverse.
A very good mobility of the cross traverse with respect to the two lever arrangements and thus a simple three-dimensional movability of the latter can be achieved if, as an advantageous further development of the invention, the two ends of the cross traverse can be connected with the respective lever arrangements by way of cardan joints.
In order to be able to compensate also possible rotating motions within the cross traverse, of the present invention may also provide that the interior element has an at least approximately round cross-section, and that the exterior tube element has a bore which has an at least approximately round cross-section and in which the interior element is accommodated.
Two or more holding devices for holding the workpieces, which holding devices can be moved independently of one another in a freely programmable manner along the cross traverse, ensure that two workpieces can be transported simultaneously and in the process can be moved independently of one another. This independent movement of the two workpieces can be used, for example, when, because of a cutting, two workpieces are created from one workpiece, the two workpieces being movable away from one another. As a result, intermediate depositing devices, which so far have been used for displacing the two workpieces, can be eliminated.
Thereby, the present invention makes possible to also, with an eccentric arrangement, to still grip workpieces such that the center of gravity of the workpiece is situated in the center of the at least two holding devices. Particularly in the case of a cross traverse, which can be moved in a space in an arbitrary manner, this is a great advantage because eccentric arrangements of the workpieces are frequently necessary particularly in such cases.
A simple possibility of independently moving the at least two holding devices can occur when the at least two holding devices can each be displaced by way of linear drives along the cross traverse.